I-10 Twin Peaks Traffic Interchange, Environmental Assessment

Affected Environment and Environmental Impacts October 2005
• Maintenance yards outside the Santa Cruz River channel would be used to
store and service construction equipment;
• No cement dumping or equipment cleaning would occur in or near the
watercourse;
• Soils that are disturbed from the Santa Cruz River channel would be
labeled and stockpiled outside the channel until construction activities are
completed. Then the soils removed from the Santa Cruz River channel
would be placed back into the areas from which they were removed; and,
• Any upland soils that are removed would moved farther upland to prevent
erosion into the Santa Cruz River.
As a result of the limited involvement of groundwater and of the proposed
precautionary practices as outlined above, EPA concurred, in a letter dated May
13, 2004, that the proposed improvements would not effect the quality of the sole
source aquifer. This concurrence letter may be found in Appendix A.
Conclusion
The preferred alternative’s impacts to the quality of surface and groundwater
resources within the study area were analyzed. This analysis determined that:
• The preferred alternative would be consistent with existing watershed and
floodplain management programs.
• The preferred alternative would be the only practicable alternative for
floodplain encroachment.
• The preferred alternative would conform to applicable State and local
floodplain protection standards.
• The preferred alternative would require an individual permit under Section
404 of the CWA and would require individual water quality certification
under Section 401 of the Act from ADEQ. Because the Section 404 permit
and Section 401 water quality certification would be obtained by the Town
of Marana prior to commencement of construction within waters of the
U.S., the preferred alternative would have no negative impacts to surface
water quality.
• An AZPDES general permit and a SWPPP, under Section 402(p) of the
CWA would be required. Because the SWPPP would be prepared and
followed during construction of the proposed improvements, the preferred
alternative would have no negative impacts to surface water quality.
• The proposed project is in compliance with Section 1424(e) of the Safe
Drinking Water Act. The project has been designed in such a manner as to
not create a significant hazard to public health, interfere with public
welfare, or cause any public water system to install additional treatment
Interstate 10 Traffic Interchange at
Twin Peaks/Linda Vista
4-24
Project No.: NH-010-D (AIW)
TRACS No.: 10 PM 236 H5838 01D